Method and apparatus for processing ceramic components

ABSTRACT

A method and apparatus for processing or cleaning ceramic components that are contaminated with dust deposits are provided. Relative vibrations are generated between the ceramic components and the ambient atmosphere for dislodging dust deposits from the ceramic components. Dislodged dust deposits are collected and conveyed away for disposal or further use. To accomplish this, a screen base is disposed within a closable chamber. A first conveyor is disposed within the chamber below the screen base and leads to a transfer station. A mechanism for generating relative vibrations is disposed between the screen base and the atmosphere of the chamber. An enclosed second conveyor leads from the transfer station to a replacable receiving vessel. An infra sound producer is disposed within the chamber.

BACKGROUND OF THE INVENTION

The present invention relates to a method for processing ceramiccomponents that have become contaminated by dust deposits, especiallycontaminated ceramic catalytic converters or catalyzers that removenitrogen.

The present invention further relates to an apparatus for cleaningceramic components that have been contaminated with dust deposits,especially contaminated ceramic catalyzers that remove nitrogen.

The invention will be subsequently explained in conjunction with ceramiccatalyzers such as are used in nitrogen oxide reduction apparatus.However, the invention can be utilized anywhere where ceramic componentsare to be cleaned and processed after they have been contaminated bydust deposits.

The flue gases from power plants, refuse incinerators and the like mustbe cleaned before they can be released into the atmosphere.

A nitrogen removal stage is integrated into the cleaning process, duringwhich the NO_(x) is reduced by the addition of ammonia, and inparticular in the presence of catalyzers. These catalyzers reduce thereaction temperature and accelerate the reduction process. They compriseceramic material, the main substituent of which is titanium dioxide. Thecatalytically active material is vanadium pentoxide or tungstentrioxide.

The catalyzers comprise so-called catalyzer elements that are embodiedas elongated honeycombed bodies and form separate, parallel flowchannels having rectangular and generally square cross-sectional areas.The catalyzer elements are combined into modules, with each modulehaving a steel frame into which the catalyzer elements are insertedparallel to one another.

By way of example, the power plant Bergkamen A (electrical capacity 750MW) is provided with two nitrogen removing reactors that are providedwith a total of 41,472 catalyzer elements, each of which has an externaldimension of 150×150×840 mm. The total weight of the catalyzer modulesis 800 t.

The useful life of the catalyzers is not unlimited. Rather, adeactivation occurs, whereby dust particles that contain noxious orharmful material are deposited upon the catalyzer walls. The rapiditywith which this occurs depends upon at which location of the flue gascleaning process the nitrogen removal is undertaken. Keeping this inmind, the most favorable location would be in an arrangement downstreamof the flue gas desulfurization apparatus, but the flue gas temperatureat this location is not sufficient for heating up the catalyzers to thereaction temperature. In this connection, a reheating of the flue gaseswould be necessary. To this extent, more favorable conditions are foundin the vicinity of the boiler upstream of the air preheater. Thisinvolves the so-called high-dust control, with which, however, thedegree of contamination of the catalyzer elements is the greatest.

By means of periodic intermediate cleaning, the useful life of thecatalyzers can be extended. For this purpose, up to now so-called sootblowers in the form of traverse blowers have been used, which areintegrated into the nitrogen oxide reduction apparatus. They comprisenozzle connections that are guided over the catalyzers and blow hotsteam into the catalyzer elements. The traverse blowers represent aconsiderable capital expenditure for apparatus. Furthermore, theeffectiveness of the cleaning also leaves something to be desired, sincethe blast energy is already dissipated after a few centimeters.

Finally, the catalyzer elements are spent and must be replaced.

The processing of the spent ceramic catalyzers represents a considerableproblem. The catalyzers are ground, whereupon in principle thepossibility exists for cleaning the ceramic material and reusing it asbase material for the manufacture of catalyzers. However, the cleaningis extraordinarily expensive because with this type of reuse, thechemical properties of the material play the important role. Inaddition, the material is not refired, but rather is merely calcined atabout 900° C. and therefore receives a strength that is less than thatof fired ceramic. Therefore, the up to now most frequently encounteredalternative is to dispose of the spent and ground catalyzers in thecontaminated state in dumps, or to supply it as an additive or filler toa slag tap furnace of a coal-fired power plant.

SUMMARY OF THE INVENTION

It is an object of the present invention to improve the intermediatecleaning of the ceramic catalyzers as well as to enable an economicaland ecological processing of the spent catalyzers.

To realize this object, the method referenced in the introductoryportion is inventively characterized in that relative vibrations aregenerated between the catalyzers and the surrounding atmosphere thatdislodge the dust deposits from the catalyzers, and in that thedislodged dust deposits are collected and conveyed away for disposal orfurther use.

In this way, the ceramic catalyzers can be cleaned in a simple andeconomical manner.

This can be effected as an intermediate cleaning within the nitrogenoxide reduction apparatus, whereby the capital expenditure for equipmentis low. The intensive cleaning effect enables a significant extension ofthe overall useful life of the catalyzers. The collection of thedislodged dust deposits is effected in a subsequently disposed electrofilter.

The method is likewise suitable for processing spent ceramic catalyzersthat can no longer be reactivated by an intermediate cleaning. Thecatalyzers are cleaned so intensively that the material thereof, aftersubsequent grinding, can be used anywhere in the ceramic industry wherethe chemical properties of the material play no role. The range ofapplication that is available is very extensive. The high value ceramicmaterial can thus be economically reused and is not lost withoutcompensation. If one takes into account the quantities that areproduced, for example as illustrated previously in conjunction with thepower plant Bergkamen A, the considerable cost advantage is obvious.

The dislodged dust deposits that collected can be disposed of in a dumpor can be conveyed to a slag tap furnace.

The relative vibrations are preferably generated as gas vibrations inthe surrounding atmosphere of the catalyzers. This process isexpediently suitable for the intermediate cleaning of built-incatalyzers but can also be utilized for the processing of spentcatalyzers. In the last-mentioned situation, a high energy input with acorrespondingly high cleaning power is effected in a limited space.

It is furthermore particularly advantageous to generate the gasvibrations in the low frequency sound range, preferably in theinfrasonic range. This allows relatively great vibration amplitudes tobe generated with relatively little expenditure of energy. The gascolumns within the catalyzer elements are thus moved correspondinglyvigorously. In addition, the infra sound spreads uniformly in alldirections, so that therefore a high debris of structural freedom isallowed. Frequencies of about 25 Hz have shown to be preferable. It hasbeen shown that the desired effect decreases with increasing frequency,whereby, however, frequencies in the range of about 100 Hz are quitepracticable. The resonance range of the nitrogen removal apparatus is at60 Hz to 70 Hz, and should, of course, be avoided.

The gas vibrations are advantageously generated by a vibration producer.In the nitrogen oxide reduction apparatus, they overlap with the flow ofthe gas that is to cleaned.

As an alternative, it is proposed in a further embodiment of theinvention to blow against the catalyzers with at least one pulsating gasstream. This corresponds to the manner of operation of a siren, wherebythe gas stream as such is in the position to enhance the cleaningeffect.

In principle, it is possible to differentiate between the cleaning ofthe complete catalyzer elements and the periodic intermediate cleaningwithin the nitrogen removal apparatus. In the first-mentioned situation,there results a very intensive cleaning effect. In the last-mentionedsituation, the particles that are not yet securely deposited on thecatalyzer surfaces are loosened and are carried out with the gas stream.Thus, involved is more a process of keeping clean than an intensivecleaning, as comes into play in the case of spent catalyzers.

It was discovered that the low frequency sound impingement of catalyzersthat are being used has a very particularly advantageous side effect,namely an increase of the catalytic effectiveness. This effect isattributable to the fact that the laminar boundary layer on thecatalyzer surfaces is pulled away and is converted into a turbulentflow. This takes place under the effect of the vibrations of theshifting gas columns. In addition, the particles that are conveyed bythe gas are hurled into the boundary layer, where they contribute to theturbulence that is imparted to them. On the whole, there results anacceleration of the material exchange processes. Ammonia and nitrogenoxides meet at higher rates on the catalyzer surfaces, so thateffectiveness thereof is increased.

The present invention utilizes these processes and proposes that thecatalyzers have sound continuously impinged upon them during their use.In this connection, it is particularly advantageous to start thecontinuous sound impingement after periodic sound impingement has beenundertaken several times.

If the catalyzers have just recently been inserted, there is frequentlyno occasion to increase their effectiveness. Only when the catalyticeffectiveness has dropped a certain amount does one start with the soundimpingement, and in particular initially with a periodic soundimpingement. The cleaning or removal achieved thereby allows thecatalytic effectiveness to again increase. If the deactivation of thecatalyzers has reached a specific extent at which the cleaning effectalone is no longer sufficient, the continuous sound impingement isinitiated. The areas of the catalyzer surfaces that have been merelydamaged relative to their effectiveness experience such a great increasein effectiveness that the useful life of the catalyzers is significantlyincreased. Frequently, a premature shut-down of the apparatus can be putoff until the next maintenance.

In an important further embodiment of the invention it is additionallyproposed that the relative vibrations be generated by vibrating thecatalyzers. This manner of operation is less suitable for theintermediate cleaning of the installed catalyzers than for processingspent catalyzers prior to their being ground and subsequently used inthe ceramic industry.

The spent catalyzers are processed externally of the nitrogen oxidereduction apparatus, whereby for reasons of environmental protection itis advantageous to suction off the ambient air that is loaded withdust-like contaminants. In so doing, pursuant to a further embodiment ofthe present invention, the suctioned-off ambient air can be cleaned,with the thereby resulting dust-like contaminants being added to thecollected dust deposits as they are conveyed away. There thus results acomplete disposal of the contaminants that are vibrated out of thecatalyzers, with such contaminants preferably being introduced into aslag tap furnace where they can be smelted to granulate.

It is particularly advantageous to vibrate the catalyzers in modularfashion. Thus, when the catalyzers are pressed out of the modules theyare already clean. This has up to now not been the case, so thatconsiderable quantities of dust were released when the modules weredisassembled.

The initially mentioned apparatus for cleaning the catalyzers isinventively characterized by

closeable chamber,

a screen base disposed within the chamber,

a first conveyor that is disposed within the chamber below the screenbase and that leads to a transfer station disposed within the chamber,

an enclosed second conveyor that starts from the transverse station andleads to an exchangeable receiving vessel that is disposed externally ofthe chamber,

a vibrator disposed within the chamber, whereby the screen base ismounted such that it is able to vibrate, or

an infra sound producer disposed within the chamber.

This apparatus is suitable exclusively for the processing of spentcatalyzers and the cleaning thereof as a preliminary step for thegrinding and the subsequent delivery of the ceramic material to theceramic industry.

The infra sound producer can be embodied as a vibration producer or as asiren that generates a pulsating air stream.

The size of the chamber is such that it respectively accommodates onemodule equipped with catalyzers. This module is placed upon the screenbase that is able to vibrate in such a way that the flow channels areoriented vertically. The preferably pneumatically operated vibratorengages or acts upon the module or upon the screen base. Due to thevigorous vibration, which is preferably carried out at high amplitudeand low frequency, the dust falls downwardly through the screen base andupon the first conveyor. This conveyor transports the dust to thetransfer station, where it is collected and taken up by the secondconveyor. The second conveyor is enclosed and leads out of the chamberto the exchangeable receiving vessel. As soon as this vessel is filled,it is taken away and replaced by an empty receiving vessel.

The cleaning effect of the apparatus is very intensive and provides thepossibility for being able to supply to the ceramic industry thematerial of the subsequently ground catalyzers.

Particularly suitable as the first conveyor is a conveyor belt, while aworm conveyor that works in a casing is in particular suitable for thesecond conveyor. The chamber protects the atmosphere against the dustthat is vibrated out of the catalyzers. In contrast, the interior of thechamber is highly charged with toxic dust that contains heavy metals. Itis therefore proposed to dispose on the chamber a suction fan that isconnected to a separator means. In this way, the dust-laden air issuctioned out of the chamber and is cleaned of the dust particles. It isfurthermore advantageous to connect the dust outlet of the separatormeans, with the chamber closed, with the first conveyor, in which casethe dust that originates with the exhaust air can be combined with thedust that falls through the screen base and can be carried off togethertherewith and disposed of.

In a further important embodiment of the invention, it is proposed thatthe chamber be provided with a horizontally displaceable hood. To openthe chamber, the hood is shifted to the side. After a cleaned module isremoved and a contaminated module is placed upon the screen base, thehood is again slid back and the chamber is thus closed. Operation of theapparatus is therefore very simple.

It is particularly advantageous to secure the separator means to thehood. As soon as the hood is shifted into its closed position, the dustoutlet of the separator means is automatically in communication with thefirst conveyor.

It is furthermore very advantageous to provide the apparatus with atravel mechanism to thereby enable a mobile application. This makes itpossible to be able to clean the catalyzers at the site of therespective power plant immediately after disassembly from the NO_(x)removal apparatus. The otherwise necessary dust proof packing of themodules is eliminated.

BRIEF DESCRIPTION OF THE DRAWING

The invention will subsequently be described in detail with the aid ofone preferred exemplary embodiment of a cleaning apparatus inconjunction with the accompanying drawing. The drawing shows in:

FIG. 1 A schematic side view of a cleaning apparatus.

DESCRIPTION OF PREFERRED EMBODIMENTS

The apparatus has a travel mechanism 1 and therefore permits a mobileuse.

The principal component of the apparatus is a chamber 2, which isprovided with a perforated bottom or screen base 3 that is mounted so asto be able to vibrate, as well as below the screen base a first conveyor4 in the form of a conveyor belt. Disposed upon the screen base 3 is amodule 5 that comprises a plurality of spent ceramic catalyzers, theflow channels of which are vertically oriented. The module 5 is engagedor acted upon by a pneumatically operated vibrator 6, which is suppliedfrom a compressor 7.

When the chamber 2 is closed, actuation of the vibrator 6 leads tovigorous vibrational movements of the module 5. In so doing, the toxicdust falls through the screen base 3 onto the first conveyor 4, whichconveys the dust to a transfer station 8. An enclosed second conveyor 9,in the illustrated embodiment a worm conveyor, removes the dust from thetransverse station 8 and conveys it into a receiving vessel 10. When thelatter is filled, it is exchanged for an empty receiving vessel.

The chamber 2 is provided with a hood 11, which is displaceable in ahorizontal direction. In FIG. 1, the hood 11 has assumed the positionwhere it is shifted toward the right, in which position the chamber 2 isopened. To close the chamber 2, the hood 11 is shifted toward the left,as indicated by dot-dashed lines.

A suction fan 12 having a separator means 13 is secured to the hood 11.In the illustrated embodiment, the separator means 13 is embodied as acyclone having a downwardly directed and angled-off dust outlet 14.During operation, the suction fan 12 conveys the air that is laden withtoxic dust out of the chamber 2 via the separator means 13, whereby thedust outlet 14 thereof is disposed above the first conveyor 4.

The apparatus permits a simultaneous and careful cleaning of all of thecatalyzers that are contained by the module. The catalyzers aresubsequently pushed out of the module, whereby there is no danger thatthe atmosphere will be contaminated with dust. The catalyzers are thenground. The degree of cleanliness of the ceramic material satisfies therequirements of the ceramic industry everywhere where the chemicalproperties do not play a role, and above all where no active catalyticproperties are required. The material can thus be supplied for asignificant and economical reuse.

Modifications are by all means possible while staying within the scopeof the present invention. For example, instead of being provided with ahood, the chamber can be provided with a hinged cover that permitsloading and unloading of a module. Filters that can be removed and/orcleaned could also be used as the separator means. Furthermore, the twoconveyors could have a different configuration. To generate thevibrational movement, it has been shown to be advantageous to allow thevibrator to engage the module. However, it is possible to introduce thevibrational movement into the screen base, whereby the module is thenfixedly connected to the latter.

Instead of using vibrational movement, it is also possible to operatewith infrasonic means. In so doing, the vibrator is replaced by an infrasound producer. In addition, there is eliminated the necessity formounting the screen base in such a way that it is able to vibrate. Theinfrasonic means operates at a frequency of about 25 Hz.

An oscillator or also an infrasonic siren can be utilized as theinfrasonic means.

Such infrasonic means can furthermore be disposed in nitrogen oxidereduction apparatus in order to carry out intermediate cleaning of thecatalyzers.

The present invention is, of course, in no way restricted to thespecific disclosure of the specificaiton and drawings, but alsoencompasses any modifications within the scope of the appended claims.

What is claimed is:
 1. A method of processing ceramic components thatare contaminated with dust deposits, said method including the steps of:generating relative vibrations between said ceramic components and theambient atmosphere for dislodging dust deposits from said ceramiccomponents, wherein said relative vibrations are generated as gasvibrations in the surrounding atmosphere; collecting dislodged dustdeposits; and conveying said dislodged dust deposits away for disposalor further use.
 2. A method according to claim 1, wherein said gasvibrations are generated in the low frequency sound range.
 3. A methodaccording to claim 2, wherein said gas vibrations are generated in theinfra sound range.
 4. A method according to claim 1, wherein said gasvibrations are generated by a vibration producer.
 5. A method accordingto claim 1, wherein said ceramic components are blown against with atleast one pulsating gas stream.
 6. A method according to claim 2,wherein said ceramic components are continuously impinged with soundduring their use.
 7. A method according to claim 6, wherein continuoussound impingement is started after periodic sound impingement has beenundertaken several times.
 8. A method according to claim 1, whereinambient air that is loaded with dust contaminants is suctioned off.
 9. Amethod according to claim 8, wherein suctioned off ambient air iscleaned and dust contaminants that thereby result are added to saidcollected dislodged dust deposits as they are conveyed away.
 10. Amethod according to claim 1, wherein said ceramic components areprocessed in modular fashion.
 11. A method according to claim 1, whereinsaid ceramic components are ground after they are cleaned and the groundceramic material is conveyed to the ceramic industry as raw material.12. An apparatus for cleaning ceramic components that are contaminatedwith dust deposits, comprising: a closable chamber; a screen basedisposed within said chamber; a first conveyor that is disposed withinsaid chamber below said screen base and that leads to a transfer stationdisposed within said chamber; a mechanism for generating relativevibrations disposed between said screen base and the atmosphere of saidchamber; an enclosed second conveyor that starts from said transferstation and leads to a replaceable receiving vessel that is disposedexternally of said chamber; and an infra sound producer that is disposedwithin said chamber.
 13. An apparatus according to claim 12, whereinsaid first conveyor is embodied as a conveyor belt.
 14. An apparatusaccording to claim 13, wherein said second conveyor is embodied as aworm conveyor.
 15. An apparatus according to claim 12, wherein a suctionfan is disposed on said chamber and is connected to a separator means.16. An apparatus according to claim 15, wherein when said chamber isclosed, said separator means communicates via a dust outlet with saidfirst conveyor.
 17. An apparatus according to claim 15, wherein saidchamber is provided with a horizontally displaceable hood.
 18. Anapparatus according to claim 17, wherein said separator means is securedto said hood.
 19. An apparatus according to claim 12, which includes atravel mechanism that enables a mobile application.